The losses were 42% higher than during the 2011-2012 winter, when 21.9% of colonies died.

California brings in honey bees from around the country for pollination at its almond farms. Almonds are a $3 billion-a-year industry. The Monterey County Beekeepers told Central Coast News that nearly two-thirds of the nation’s bee colonies in the U.S., from as far away as Florida and the East Coast, are shipped to the state.

The beekeepers group estimated that 65% of the bees died this past winter. As the bee population declines, California growers have to spend more money to obtain them, which is reflected in higher food prices.

Experts noted that the latest losses were in line with the average die-off of 30.5% over the past six years. A loss rate of 15% is considered “acceptable,” according to beekeepers, but 70% of the 6,000 beekeepers surveyed in the study cited heavier losses than that.

Bees have been dying in significant numbers in recent years without explanation. The best that experts and the government can do is give the problem a name: Colony Collapse Disorder.

The USDA says the causes could be parasites, disease, genetics, poor nutrition or pesticide exposure. Environmental and beekeeper groups sued the Environmental Protection Agency last March, seeking to ban pesticides that have been found toxic to bees. The European Commission recently announced it will be banning, across the entire continent, three insecticides believed to be killing Europe’s bee colonies: imidacloprid and clothianidin, produced by Bayer, and thiamethoxam, produced by Syngenta.

There are an estimated 2.62 million bee colonies in the United States.